Noncontact IC media capable of performing communication of information stored therein in a noncontact manner are conventionally utilized. Such noncontact IC media include a medium using a UHF band available for long-distance communication. In most cases, a single-element patch antenna is used as an antenna for communicating with the noncontact IC medium using the UHF band. The single-element patch antenna has a half-power width (beamwidth) as broad as about 70 and therefore has the advantage of reading information from the noncontact IC media in a broad area.
Meanwhile, there has been proposed a tag communication device that calculates the position of a noncontact IC medium on the basis of estimated incoming direction of a radio wave from the noncontact IC medium (see Patent Literature 1). The tag communication device applies different weights to outputs of antenna elements to detect the intensity of the radio wave in a specific direction.
However, the tag communication device requires complicated calculations in order to find the direction where one noncontact IC medium exists. In addition, the tag communication device is affected by the presence of a reflective object, which requires correction of direction error caused by the reflected object. Thus, the tag communication device cannot easily realize obtaining of the direction where the noncontact IC medium exists.
Patent Literature 1
Japanese Patent Application Publication, Tokukai, No. 2006-10345 A (Publication Date: Jan. 12, 2006)